Cost-effective sensors for measuring the steering wheel angle supply relative values which give the angle of the steering wheel related to the steering wheel position at the starting of the ignition of the motor vehicle. Irrespective of whether a center position of the steering wheel is present at the starting of the ignition (that is to say at the start of a journey), the steering wheel angle sensor displays a zero value or a random value at the beginning. In general, the measured steering wheel angle therefore differs from the actual steering angle by a fixed angle, i.e. a zero point shift or offset of the steering wheel at the start of ignition, which actual steering angle is zero degrees in the case of straight-ahead travel of the vehicle, that is to say a center position of the steering wheel. However, for the safety of the vehicle precise knowledge of the actual steering angle is indispensable since the latter constitutes an essential measurement variable for vehicle dynamics control systems such as a yaw moment controller (ESC). It is therefore necessary to determine and to correct the zero point shift of the measured steering wheel angle.
DE 697 14 806 T2, which is incorporated by reference, (and the corresponding U.S. Pat. No. 5,790,966, which is incorporated by reference) discloses a method for determining the position of a steering wheel in which the center position of the steering wheel is estimated with a first predefined algorithm or a second predefined algorithm, depending on whether a calculated steering wheel lock angle is inside or outside a certain interval. Relatively fast or relatively slow settling at a center position value occurs depending on the algorithm used.
DE 10 2008 063 567 A1, which is incorporated by reference, discloses a steering lock angle determining system for the fast and precise determination of the zero shift of a measured steering angle and therefore a fast and precise determination of the actual steering lock angle or steering angle of a vehicle. A calculated steering lock angle is determined from a measured yaw rate and the derivative of said steering lock angle over time is calculated. Furthermore, the derivative of the measured steering angle or steering lock angle over time is determined. If the deviation between the derivation of the measured steering lock angle and the derivation of the calculated steering lock angle undershoots a first threshold, the measured steering lock angle is corrected on the basis of a calculated steering lock angle, and otherwise the measurement and the subsequent calculations are repeated. Since the determination of the calculated steering lock angle is based on the known single-track model of a vehicle, it can be applied only under certain conditions, as described in M. Mitschke, Dynamik der Kraftfahrzeuge [Dynamics of Motor Vehicles], Volume C Fahrverhalten [Driving behavior], Springer, 1990, which is incorporated by reference. In the steering lock angle determining system there is provision for the quality of the correction to be described by means of a confidence interval. However, it has become apparent that this does not indicate with sufficient reliability whether the correction is valid.